Convolutional Neural Network Models Combined with Kansei Engineering in Product Design

This study aims to combine deep learning technology and user perception to propose an efficient design method that can meet the perceptual needs of users and enhance the competitiveness of products in the market. Firstly, the application development of sensory engineering and the research on sensory engineering product design by related technologies are discussed, and the background is provided. Secondly, the Kansei Engineering theory and the algorithmic process of the convolutional neural network (CNN) model are discussed, and theoretical and technical support is provided. A perceptual evaluation system is established for product design based on the CNN model. Finally, taking a picture of the electronic scale as an example, the testing effect of the CNN model in the system is analyzed. The relationship between product design modeling and sensory engineering is explored. The results show that the CNN model improves the “logical depth” of perceptual information of product design and gradually increases the abstraction degree of image information representation. There is a correlation between the user perception impression of electronic weighing scales of different shapes and the design effect of product design shapes. In conclusion, the CNN model and perceptual engineering have in-depth application significance in the image recognition of product design and the perceptual combination of product design modeling. Combined with the CNN model of perceptual engineering, product design is studied. From the perspective of product modeling design, perceptual engineering has been deeply explored and analyzed. In addition, the product perception based on the CNN model can accurately analyze the correlation between product design elements and perceptual engineering and reflect the rationality of the conclusion.


Introduction
With the continuous improvement of people's material life, the products provided by society are more and more abundant. Te products consumers want to choose from are restricted to varying degrees. Kansei Engineering is the mainstream direction of future products and has been recognized by more and more people. Products designed by Kansei Engineering can often stand out among similar products [1,2]. In order to make the designed products conform to the living habits of consumers, product design is integrated into consumer participation, diversifcation, and life guidance [3]. In 1987, Mazda was the frst in the automotive industry to set up the "Kansei Engineering Laboratory" and applied the research results to the new Miata MX5. Tis new type of application demands a perceptual image of intimacy, maneuverability, and speed. Finally, the Miata MX5 went to Japan and the USA, and sales improved. Te brand's huge success has sparked interest and attention from all walks of life in Kansei Engineering in product design. In the next 30 years, Kansei Engineering has achieved remarkable results in various product felds, especially in the felds of clothing, architectural decoration, sanitary ware, and home furnishing [4,5]. In 2013, Yi Ning Sanitary Ware also established a Kansei Engineering research department to research faucet showers and other products [6]. Sharp's market share in the video camera segment increased from 3 percent to 24 percent after it introduced a new video camera that uses a liquid crystal display (LCD) to replace traditional eyepieces. Te camera uses Kansei Engineering techniques [7]. Te Wacoal Company is an underwear manufacturer. It collects perception data on the use of ordinary underwear and develops a new product based on these data, which has a market share of 42% in Japan [8]. Perception is one of the key factors for a product to be successful in the market. Whether a product is excellent is largely related to users' subjective perception. When designers design a product, a product that is sufciently useful and innovative will not really be successful if the product does not generate a good perception among users.
Sun et al. took the mobile phone modeling design as an example, took the user's perceptual needs as the starting point, and proposed a user preference balance method based on the multi-dimensional surface method. Te design balances the diferent preferences of users in the same product [9]. Kang cited the rough set theory for designing products perceptually [10]. Zeng et al. used the neural network model and gray relational analysis model as the design basis to guide the design of mobile phone modeling. Compared with the gray relational analysis model, the neural network model can better guide the design process, design the best mobile phone modeling elements, and meet the consumer's design image of the product [11]. Ayyildiz et al. used fuzzy rules to design ofce chairs to satisfy consumers' satisfaction with the product and established a relationship model between consumer satisfaction and design elements [12]. Einfalt et al. used a neural network algorithm to analyze whether the product contains the sensory feature of Scottish Whisky to classify the application of the product [13]. Mou et al. used imagery and other methods to describe the feeling of a product. Tey believed that when designing a product, designers should design based on the needs and feelings of the user groups of the product [14]. Bayih et al. took the product design of the baby guardrail as the object and established a mutual mapping model between the color design scheme of the product and the manual evaluation of the scheme through gray theory and neural network technology theory [15]. Gao et al. made a program refnement of the hierarchical inference method of Kansei Engineering and used it to guide the design of farm vehicles [16]. Han et al. used the back propagation neural network (BPNN) algorithm to propose a color-matching method. Te proposed method can perform the color conversion in diferent spaces and solves the color conversion between red, green, blue (RGB) and cyan, magenta, yellow, black (CMYK) space [17].
Tese studies illustrate the feasibility of neural network models in product design. Still, there is no application research on the fusion of consumer perception of products and neural network models in product design. In order to demonstrate the impact of Kansei Engineering and convolutional neural network (CNN) on product design applications, frstly, the product design application development and related technologies of Kansei Engineering are discussed to provide a background for the research. Secondly, the Kansei Engineering theory and the algorithm process of the CNN model are discussed, and theoretical and technical support is provided. A perceptual evaluation system for product design based on a convolutional neural network (CNN) model is established. Finally, taking a picture of the electronic scale as an example, the testing efect of the CNN model in the system is analyzed. Moreover, the relationship between its product design modeling and sensory engineering elements is explored and analyzed.

2.
1. An Overview of Kansei Engineering Teory. Kansei Engineering is the combination of Kansei Engineering and user perception. In the early stage, some scholars conducted research on "Kansei Engineering" and believed that Kansei Engineering is a kind of subjective sensory impression obtained by individuals from an artifcially produced product or environment by using users' perception (vision, hearing, smell, taste, recognition, and balance). Terefore, Kansei Engineering can also be called "sense engineering" or "afective availability" [18]. Its main purpose is to quantify the user's psychological feelings, transform them into perceptible design elements, and transform ergonomic knowledge into understandable design features, and is a technology that transforms users' perceptions into design specifcations [19]. Kansei Engineering uses methods from psychology, ergonomics, medicine, or engineering to calculate in the process. It is a discipline that transforms perceptual cognition into design parameters and specifcations. It aims to improve people's pursuit of happiness and emotional satisfaction in the quality of life. Kansei Engineering is a technique that combines perception and engineering. It mainly designs products by analyzing people's feelings and manufactures products according to people's preferences. In Kansei Engineering, Kansei is a dynamic process that changes with time, fashions, trends, individuals, and personalities, and it is not easy to quantify. However, as a basic perceptual process, it can be measured, quantifed, and analyzed by modern technology. When designing a product, Kansei Engineering frst needs to decompose the picture of the sample to be tested into several pairs of descriptive graded adjectives. After the subjects are judged, diferent adjectives are selected for statistical induction of diferent levels of the pictures. Ten, the perceptual results of the product are derived. Finally, the results are used for product design reference or product evaluation. Kansei Engineering-user perception cognitive design application process is shown in Figure 1.
In Figure 1, frstly, consumers' perceptual demands for products are obtained through research, experiment, analysis, and other methods. Surveys or experiments are used to determine the design elements of the product. Computeraided technology builds sensory engineering systems, such as artifcial intelligence, neural networks, general algorithms, and fuzzy logic. Te Kansei Engineering system is regularly adjusted according to the development trend of social product design and personal preference, and the perceptual database is updated during this period. Kansei Engineering uses engineering methods to quantify human sensibility, including physical and psychological product perception, to fnd the relationship between each perception and engineering, and to design and develop products. Kansei Engineering takes consumers' emotional responses and cognition as the basis of research. It constructs products that conform to consumers' feelings and intentions through statistical analysis and the operation of computer technology. Te main goal of Kansei Engineering is to identify which element of product design can elicit a particular perceptual response to the use of the product by consumers and then strive to include that element in product design. Te generation of consumers' intrinsic sensibility depends not on one design element but the combination and balance between multiple design elements [2]. Te main research contents of Kansei Engineering are shown in Figure 2.
In Figure 2, sensory analysis physiology mainly studies the source of human sensibility, focuses on the research from the perspective of physiology, and uses statistical methods to evaluate human sensibility through the measurement and test of sensibility. Perceptual informatics is processing data information based on a computer. Te output result is the secondary information needed by decision-makers to realize the conversion between perceptual and physical quantity. Kansei Creation Engineering mainly evaluates the efectiveness, usability, operation, and promotion for the purpose of product use, so as to achieve the design and manufacture of products that meet the needs of consumers. Sensibility is a variety of human feelings and images of objects, including the fve basic human senses: touch, hearing, sight, smell, and taste. In terms of measuring the fve senses of human beings, according to the diferent directions of technology, the classifcation of Kansei Engineering is shown in Table 1.
According to the defnition and classifcation of Kansei Engineering, the content of Kansei Engineering can be summarized as the relationship between people and things. Kansei Engineering − the relationship between people and things is shown in Figure 3.
In Figure 3, the physical and psychological feelings between people and objects are further analyzed. Trough the study of the fve senses of human beings, product design and other issues are improved, which is coordinated with people's various sensory and psychological needs so that people's fve senses are in a suitable "comfort zone." Te optimal design scheme to reduce physical and energy consumption is selected so that various physiological and psychological processes that occur in human labor and life are in the best state [20]. Improving the perceptual experience of product design for consumers has become a consensus in the design community. Kansei Engineering provides a design method that can improve the competitiveness of products by transforming consumers' perceptual demands into product design elements. Based on the above relationship between Kansei Engineering people and products, the Kansei Engineering system is shown in Figure 4.
In Figure 4, the system is an expert system composed of a database with perceptual information content and correct logical reasoning ability units, which can perform conversion work between physical and perceptual quantities. Kansei Engineering systems can be divided into "forward" and "reverse Kansei Engineering systems" [21][22][23]. Te "forward-type Kansei Engineering system" can transform people's perceptual needs into product design elements for product design and development. Its main purpose is to construct the relationship between consumers' perceptual needs and product design elements, and the expert system constructed from the results is used for product design demand consultation. However, in the process of product design, the reverse type sometimes requires perceptual analysis of product design concepts, design drawings, and schemes. Terefore, the "inverse Kansei Engineering system" is an inverse system that predicts the user's sensibility toward design drawings and concept drawings.

Te Process of the CNN Model Algorithm.
Convolutional neural network (CNN) is a very common algorithm model in deep learning and is widely used in image processing. A complete CNN can contain convolutional, pooling, fully connected layers, etc. Convolutional layers are used for feature extraction, and pooling layers are used for dimensionality reduction. Fully connected layers can be used for outcome prediction [24]. Te basic structure of CNN is shown in Figure 5.
In Figure 5, the mirror on the left is the input layer, and the computer understands that it inputs several matrices. Te convolutional layer uses rectifed linear unit (ReLU); the Computational Intelligence and Neuroscience convolutional layer is followed by a pooling layer; the pooling layer has no activation function. Te combination of convolutional and pooling layers can appear multiple times in the hidden layer. In practice, this number is based on the needs of the model. Te convolutional and pooling layers are fully connected layers. Te output uses a Softmax activation function for image recognition classifcation [25,26]. Te activation functions are shown in In equation (1), the output of the ReLU function is either 0 or a positive number. Te ReLU function is not a 0-    Computational Intelligence and Neuroscience centered function. In (2), Softmax(x) is multi-class problem where more than two class tags require class membership. For any real vector of length K, the Softmax function can compress it into a real vector of length K with values in the range [0, 1], and the sum of the elements in the vector is 1. For a certain convolutional layer, the activation functions used by diferent feature maps are the same. But the activation functions used by diferent convolutional layers can be diferent. Te core of CNN is the convolution operation, which is equivalent to the "flter operation" in image processing. For a convolution kernel of size m × n, W � w 11 w 12 · · · w 1n w 21 w 22 · · · w 2n · · · · · · · · · · · · w m1 w m2 · · · w mn , the calculation of the convolution operation on an image X is shown in Z � w 1 x 1 + w 2 x 2 + · · · + w mn x mn � W T * X.
In (3), each weight w in the convolution kernel W is multiplied by the corresponding pixel x in the covered original image X. Te sum is obtained to obtain the convolution operation result of the convolution kernel. For the  Computational Intelligence and Neuroscience complete convolution operation process of an image, the convolution kernel slides at a certain interval, performs convolution operation on the coverage area, and obtains the Z value until the entire image is traversed. Te complete convolution operation process is shown in Figure 6.
In Figure 6, the input is a two-dimensional 3 × 4 matrix, and the convolution kernel is a 2 × 2 matrix. Assuming the convolution is done by shifting one pixel at a time, the upper left corner of the input 2 × 2 is convolved with the convolution kernel. Te elements of each position are multiplied and added to obtain the element output matrix Z of Z 00 , and the value is aw + bx + ey + fz. Ten, the input part is shifted one pixel to the right. A matrix consisting of (b, c, f, g) four elements and a convolution kernel is convolved. Te element matrix Z of the output Z 01 is obtained. Te same method is used to obtain the elements of Z 02 , Z 10 , Z 11 , Z 12 of the output matrix Z. Finally, the convolution output is a 2 × 3 matrix Z [27], as shown in In (4), n in is the number of input matrices or the dimension of the last dimension of the tensor. X k represents the kth input matrix. W k represents the kth kernel matrix of the convolution kernel. Z ij represents the value of the corresponding position element of the output matrix corresponding to the convolution kernel. Te data size calculation after convolution is shown in In (5), n is the size of the original image; p is the number of flled pixel columns at the edge of the original image; and f is the size of the convolution kernel of the flter. Te original image has only one channel, so only one kernel is used for convolution f. S is the moving step size of the flter on the image.
If Δ � z − y is used to calculate the error, Δ is the error of the back-propagated layer back. Te error is back-propagated to the previous neuron, and the weight is frst multiplied to get the error of a neuron. Te operation process of the pooling layer is shown in Figure 7.
In Figure 7, the stride is 2. Usually, for every n × n element of the input submatrix to become one, the pooling criterion is required to assign it max or average. Te maximum or average value of the corresponding region is used as the element value after pooling. Image samples are input. Te L layer and the types of all hidden layers are calculated by the output of the CNN model, and the output calculation of the pooling layer is shown as follows: In equation (6), pool is the process of reducing the input tensor according to the pooling area size K and the pooling standard; a l−1 is to fll the edge of the original image according to the flling size P of the input layer and the obtained input tensor. Te output of the fully connected layer is shown in Equation (7) corresponds to that the lth layer is a fully connected layer; σ is the activation function. Sigmoid and tanh are desirable. After several fully connected layers, the last layer is the Softmax output layer. At this time, the calculation expression of the output layer is shown in Te step size of the input gradient iteration parameter is α; the maximum number of iterations and the stop iteration threshold is ϵ; the loss function is used to calculate the output δ i,l of the fully connected layer. Te updated calculation of W l and b l of the lth layer of the fully connected layer is shown in

Application Research of Product Design Taking Electronic
Weigher as an Example. Electronic scales are mainly composed of three parts: load-bearing (such as weighing pan and scale body), force transmission (such as lever force transmission system and sensor), and indication (such as dial and electronic display instrument). According to the structural principle, it can be divided into three categories: mechanical, electronic, and electromechanical scales [28]. Te perceptual evaluation system of product design based on the CNN model is shown in Figure 8. Figure 8 mainly uses the semantic diference method to grasp the consumer's sensibility and statistical analysis to process the data to establish the correlation between the consumer's sensibility and product design elements. Tis association is used to guide steps such as the design process. Firstly, market research determines the target consumer group and product development goals. Secondly, the perceptual semantic space is expanded to accurately grasp the perceptual demands of consumers for the product to be tested. Product features and various design elements are determined, and the product feature space is expanded. Finally, the CNN model is used to measure the perceptual evaluation of product design.

Analysis of CNN Model Training Results.
Te initial learning rate is set to 0.01 based on all the images of electronic scales in the market, enterprises, and magazines as training samples. Impulse is set with a parameter of 0.9 and decays by a ratio of 1e − 6 per iteration. Te training process lasts for 12 rounds, and each round feeds all training samples into the CNN model for iteration. Te analysis of the training results of the CNN model is shown in Figure 9.
In Figure 9, the average accuracy of CNN on the test set is 81.96%. As the number of training increases, the accuracy of CNN training in this system gradually increases, with a correct rate of 96.12%. Its training loss value is also gradually decreasing, and the loss rate is as low as 2.01%. Te CNN model improves the "logical depth" of the perceptual information of product design and gradually increases the abstraction degree of image information representation.

Analysis of Kansei Engineering Elements of Product Design: Electronic
Weigher. Many samples collected in the market, enterprises, and magazines are analyzed and screened. Tey are divided into four groups according to the product design and shape of the electronic weighing machine. Figure 10 shows the score results of the Kansei Engineering elements of the electronic scale.
In Figure 10, the perceptual words of sample No. 1 tend to be simple, reliable, and tough, and also give people a sense of precision, a strong sense of technology, and stability. Te perceptual vocabulary of sample No. 2 is simple, high end, and humanized. On this basis, it will give people a sense of fashion, liveliness, and easy operation. Te perceptual vocabulary of sample No. 3 tends to be high end and humanized, while other perceptions tend to be simple, slightly  Computational Intelligence and Neuroscience cute, easy to use, and fresh. Te perceptual vocabulary of sample No. 4 is humanized, and it will give people the perception of being easy to use, fresh, and fashionable. Tere is a correlation between the user perception impression of electronic weighing scales of diferent shapes and the design efect of product design shapes.

Conclusions
Combining perceptual engineering and CNN models, product design applications are studied. Te electronic weighing scale picture is used as an example, and the training efect of the CNN model in the perceptual evaluation system of product design is analyzed. Based on the shape design of the electronic weighing machine, the scoring results of diferent electronic weighing machine shapes in the perceptual engineering elements are analyzed. Te results show that the accuracy rate of CNN training in the perceptual evaluation system of product design is gradually improved, and the correct rate is 96.12%. When analyzing the perceptual engineering elements of electronic weighing scales, the user perception impressions of electronic weighing scales with diferent shapes are related to the design efect of product design modeling. When neural networks are used to assess the morphological imagery of the goblet, there is a correlation between the shape design of the goblet and the perceptual imagery. Tis is consistent with research fndings demonstrating a correlation between product design styling and user perceptual imagery. In addition, when using the neural network model to evaluate the perceptual product design, the neural network model can evaluate the perceptual product design but does not analyze the training efect of the neural network. Tis study proves the correctness and convergence of the CNN model in the training efect. Te CNN model is used to improve the "logical depth" of information in the perceptual feld of product design and gradually increase the abstraction level of image information representation. Te CNN model can accurately analyze the relationship between product design elements and perceptual engineering and refects the rationality of the research on the side. In addition, combined with the research on product design of the CNN model of perceptual engineering, the understanding of perceptual engineering has been deeply explored from the perspective of product design. Consumer perception of the product is taken as the design concept of the product. Consumer perception and perceptual engineering and CNN models are integrated to provide designers with a design experience close to consumers' sensibilities. However, some defciencies still exist. Tis study analyzes the perceptual engineering results of product design from the perspective of modeling and does not comprehensively study the color, texture, and material of product design. Tese product design elements all afect consumers' perception of the product. In the future, product design elements will be used as a starting point, and the application of perceptual engineering will be expanded accordingly. Combined with the development of neural network technology, the product design of perceptual engineering is analyzed more comprehensively.

Data Availability
Te data used to support the fndings of this study are available from the corresponding author upon request.

Conflicts of Interest
Te authors declare that they have no conficts of interest. Computational Intelligence and Neuroscience 9